DIRECT MEASUREMENT OF HIGH FREQUENCY SOLID PROPELLANT PRESSURE COUPLED RESPONSES.

This paper presents an experimental method that is capable of directly measuring solid propellant pressure-coupled responses at the high frequencies associated with tangential mode instabilities. The method utilizes a magnetic flowmeter to measure the velocity oscillation above a burning propellant surface within an externally excited combustion chamber. A magnetic flowmeter burner was designed and constructed to evaluate the method of pressure-coupled response measurement. Response measurements were obtained for two formulations of AP/HTPB composite propellant at pressure oscillation frequencies of 4000 and 8000 Hz. The measurement data displayed consistent trends in both the real and imaginary parts of the pressure-coupled response function.